The automatic forming of glass articles, particularly containers such as bottles and jars, is performed in the so-called "I.S. machines" that are well known in the art and which generally are made up of eight sections of one or several cavities located beneath a glass feeder which supplies them with gobs of molten glass for the purpose of forming the articles.
Each section of the forming machine comprises approximately nineteen mechanisms which operate sequentially to carry out a predetermined forming function and which are also synchronized in predetermined forming cycles with respect to the other individual sections of the machine.
The element required to synchronize all the mechanisms of the machine is the well known Mechanical Timing Drum.
At the present time, such mechanical timing drums have been replaced by electronic controls which tend to impart a more precise synchronization to the actuation of the mechanisms of each section of the machine, thereby allowing the response speed of the mechanisms to be considerably increased and, as a consequence, the production rate of articles to be raised.
However, both the mechanical timing drums and the present-day electronic controllers have a difficulty relating to the adjustment of the timing of each mechanism and the successive repetition of the forming cycles.
In U.S. Pat. No. 3,762,907 by Quinn et al, there is described and claimed an electronic control system for performing the operation of automatic synchronization of the machine sections using a shaft encoder coupled mechanically to the machine, so as to generate the necessary pulses to cause the mechanisms to be fired synchronously with the machine as determined by the synchronization shaft.
In said controller, pulses may be lost from causes such as the wearing of the mechanical parts of the encoder and failures in the mechanical linkage of the parts thereof, so that the several sections of the machine lose their synchronization, the mechanisms knocking against each other on not being properly synchronized in their operation as a result of the time limits among them not being observed.
On the other hand, said control lacks flexibility since, although it is possible to increase the speed of gob cutting and of forming by increasing the rate at which the encoder generates pulses, there is no capacity for automatically changing the speed of operation of the mechanisms of the machine sections consequent upon changes in cycle (times) during the operation of the machine.
In Mexican Pat. No. 145,266 (U.S. Pat. No. 4,108,623) held by the same licensee as the present applicant, there is described and claimed an electronic control system consisting essentially of a pre-programmed controller for sequentially controlling all the forming operations of the machine, a generator of pulses of constant frequency to operate as a real-time clock to measure the time and duration of each operation controlled by the controller, a gob detector which detects the moment at which a gob coming from the glass feeder is cut so as to inform the controller of the ending of a previous cycle and the beginning of a new one, and a temperature detector to detect the passage of the gob toward the mold and to inform the controller thereof so as to trigger the forming cycle of the corresponding section.
Said controller calculates the time taken by a gob from its cutting in the glass feeder to its reception in the mold of whatever section, and on this basis calculates the total cycle time of the machine with its first speed parameters, in such a way that, as the cutting and transportation of the gob continue to be detected the mechanisms of each section of the machine are allowed to function properly and in a synchronous manner with the total cycle initially calculated by the control.
In this way, on receiving the signal from the gob cutting sensor, even though the gob passage signal be lost, the control is enabled to command the forming cycle of the section concerned, the new cutting signal being available for the remainder of the sections.
Nevertheless, this control calculates the cycle time only at the beginning or start-up of the whole machine, but does not have the capability to calculate and keep it current with changes in the forming cycle times, so that, once the cutting signal has been lost, collisions among the mechanisms of the machine and, finally, the maladjustment of such mechanisms, may be caused.
Furthermore, said control does not have the capability to calculate a new forming cycle in case of variations in said cycle, thus again causing collisions among the mechanisms.
In view of the limitations of the prior art, the inventor of the present invention developed an intelligent digital controller for predicting and automatically compensating for timing variations, in machines for forming articles of glass, which controller is not mechanically linked to the machine and, consequently, does not include mechanical parts susceptible to wear (as in the mechanical encoder) whereby the operation of the machine and the gob distributor might get out of phase one with the other.
The intelligent controller of this invention continually recalculates the cycle time and the waiting time so that, if the signal from the gob sensor should not arrive, a firing signal is generated within the latest calculated cycle and stepped adjustments are made in the timing of the mechanisms as a function of the latest calculated cycle and in accordance with the dead times of the mechanisms, in order to prevent the new forming cycles from overlapping and the mechanisms from colliding so that, when the gob sensor once again sends a signal, said signal is used as a new point of reference.
Furthermore, since the subject invention includes at least one real-time data processing unit the memory whereof contains a mathematical model which calculates the initial forming cycle time and the operation time of the forming mechanisms of the machine, compares them with the present and past operation times and initiates the next forming cycle in all the sections of the machine, said invention compensates for variations in the periods of the cycle time.
Said real-time processing unit may be considered as an independent prediction and compensation computer and supplies prediction and compensation data to each one of the processors, corresponding to each machine section, of the central or master controller, for the purpose of actuating the mechanisms in accordance with the control program of the central or master controller and with the data from the prediction and compensation computing processor.
On the other hand, when the processors corresponding to each section of the machine have time and capacity to make the prediction and compensation calculations, the corresponding processor will become integrated with each one of said individual processors of the central or master control, for each section of the machine.